A lithium-ion battery

Abstract

The application relates to the technical field of batteries, in particular to a lithium ion battery. The lithium ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte; the negative electrode comprises a negative electrode current collector and a negative electrode material layer arranged on the surface of the negative electrode current collector; the non-aqueous electrolyte comprises a lithium salt, an organic solvent, a sulfur-containing compound, a difluorophosphate ion and an oxalate complex anion; the lithium ion battery satisfies the following conditions: 0.05 <= a / c <= 15, 0.05 <= b / (cxd) <= 20, 0.01 <= a <= 1, 0.01 <= b <= 1.2, 0.01 <= c <= 0.8 and 0.5 <= d <= 15. The lithium ion battery can fully exert the advantages of the oxalate complex anion in reducing the battery impedance and forming a high-stability LiF-rich interface film, and can simultaneously improve the initial adhesion between the negative electrode material layer and the negative electrode current collector, offset the deterioration of the adhesion caused by micro-gas production, and realize the balance between the impedance agent and the fast-charging cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a lithium-ion battery that has fast charging cycle performance while also having low impedance. Background Technology

[0002] To mitigate the impacts of climate change and air pollution, the widespread adoption of lithium-ion batteries in pure electric vehicles is accelerating. However, compared to traditional gasoline vehicles, range anxiety and long charging times remain major obstacles to the development of electric vehicles. Therefore, improving fast charging capabilities has become an urgent development goal for both battery manufacturers and vehicle manufacturers.

[0003] Lithium-ion batteries mainly consist of four key components: the positive electrode, the negative electrode, the electrolyte, and the separator. Numerous studies have shown that the degradation of the positive electrode and the growth of the SEI (Sediment Electrode Injection) film do not affect the fast-charging speed of traditional lithium-ion systems. Therefore, the lithium-ion migration capability of the negative electrode, especially the SEI interface film, has become a major research focus. Research indicates that the chemical composition of the SEI film is closely related to the electrolyte composition. Based on the current conventional carbonate solvent and lithium hexafluorophosphate-based electrolyte system, the inner layer of the SEI film near the electrode interface is dominated by stable and dense inorganic materials such as Li₂CO₃, Li₂O, and LiF, while the outer layer near the interface is dominated by loose and porous organic materials such as ROLi and ROCO₂Li. LiF is considered one of the key components affecting the stability of the interface film. By adjusting the electrolyte additives (such as LiPO₂F₂) and other components, the abundance of LiF in the interface film can be altered to achieve better high-temperature performance. However, LiF, as an inorganic component, does not inherently possess good lithium-ion migration capabilities. Multiple studies have indicated that the distribution of components in the SEI film exhibits a "mosaic model" characteristic, and lithium-ion migration within the inner interfacial film relies on the migration between different component interfaces. Among these, the LiF / Li₂CO₃ interface is a key feature affecting the ionic conductivity of the interfacial film; a higher LiF interface significantly reduces film impedance, thereby improving the fast-charging capability of lithium-ion batteries. Therefore, developing a lithium-ion battery capable of forming LiF-rich layers with low film impedance is of great significance for balancing battery impedance and excellent fast-charging cycle performance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a lithium-ion battery with excellent fast-charging cycle performance and low impedance.

[0005] The present invention adopts the following technical solution:

[0006] A lithium-ion battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte;

[0007] The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on the surface of the negative electrode current collector;

[0008] The non-aqueous electrolyte includes lithium salts, organic solvents, sulfur-containing compounds, difluorophosphate ions, and oxalate complex anions;

[0009] The sulfur-containing compound includes at least one of the following compounds:

[0010]

[0011] The lithium-ion battery meets the following conditions:

[0012] 0.05≤a / c≤15, 0.05≤b / (c×d)≤20; and 0.01≤a≤1, 0.01≤b≤1.2, 0.01≤c≤0.8, 0.5≤d≤15;

[0013] Where a is the mass percentage of sulfur-containing compounds in the non-aqueous electrolyte, in wt%.

[0014] b represents the mass percentage of difluorophosphate ions in the non-aqueous electrolyte, in wt%.

[0015] c represents the mass percentage of oxalate complex anions in the non-aqueous electrolyte, in wt%.

[0016] d represents the bonding force between the negative electrode material layer and the negative electrode current collector, measured in N / m, and is obtained by testing according to the national standard GB / T2790-1995, "180° Peel Strength Test Method for Adhesives".

[0017] The lithium-ion battery of this invention uses a sulfur-containing compound as an additive in the non-aqueous electrolyte, and contains difluorophosphate ions and oxalate complex anions. Through extensive research, the inventors discovered that when the mass percentages of the sulfur-containing compound (a), difluorophosphate ions (b), and oxalate complex anions (c) in the non-aqueous electrolyte, and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector satisfy the following relationships: 0.05 ≤ a / c ≤ 15, 0.05 ≤ b / (c × d) ≤ 20; and 0.01 ≤ a ≤ 1, 0.01 ≤ b ≤ 1.2, 0.01 ≤ c ≤ 0.8, 0.5 ≤ d ≤ 15, the battery can achieve both low initial impedance and excellent high-temperature fast-charge cycle performance. It is speculated that the oxalate complex anion, as an electrolyte additive, can reduce impedance. On the one hand, due to its very low film-forming potential, most of the oxalate complex anions can participate in film formation in advance, and the fluorinated oxalate complex anions can increase the abundance of LiF in the interfacial film. More importantly, the presence of the oxalate structure can form more Li2CO3 components, which, when used in combination with difluorophosphate ions, can significantly increase the abundance of LiF and provide more LiF / Li2CO3 interfaces, enabling lithium-ion batteries to balance impedance and excellent high-temperature performance. On the other hand, oxalate complex anions usually have a cyclic structure, which allows them to complex with transition metal ions dissolved from the positive electrode, thereby reducing the damage of metal ions to the SEI film and the catalytic decomposition of the electrolyte, inhibiting impedance growth and ensuring the long-term performance of the battery.

[0018] Although oxalate complex anions play an important role in regulating membrane composition, the Li2CO3 component has poor oxidation resistance and may be converted into CO or CO2 under high voltage, leading to electrode separation or a decrease in the adhesion between the negative electrode material layer and the negative electrode current collector. This can result in uneven lithium intercalation in the battery or hinder electron conduction between the negative electrode material layer and the current collector. Furthermore, the addition of oxalate complex anions to the battery electrolyte increases the electrolyte acidity, which may attack the interfacial membrane or corrode the negative electrode current collector, thus degrading battery performance.

[0019] To address this issue, the inventors, through extensive research, discovered that the negative electrode fabrication process can be controlled to achieve higher initial adhesion, thereby offsetting the negative impact of reduced adhesion between the subsequent negative electrode material layer and the negative electrode current collector. The sulfur-containing compound can also decompose to produce Li₂CO₃ components, but it also generates more sulfur-containing components and polyethylene oxide (PEO)-like structural components, resulting in better stability and reduced gas production from Li₂CO₃ decomposition. Furthermore, it has a strong binding effect with fluoride ions, inhibiting the growth and negative effects of HF. The film-forming potential of the sulfur-containing compound is higher than that of difluorophosphate ions and oxalate complex anions, meaning its film formation occurs later, protecting the stability of other film-forming components and improving the toughness of the inorganic outer layer, reducing film damage caused by electrode volume changes during cycling. Therefore, the lithium-ion battery of this invention utilizes the order of film formation of different materials and the characteristics of the components to control the formation of a low-impedance and more stable negative electrode interface film. Combined with the pre-controlled formation of higher adhesion between the negative electrode material layer and the negative electrode current collector to offset the degradation caused by micro-gas production, it ultimately achieves a balance between battery impedance and fast-charging cycle performance.

[0020] When the mass percentage of sulfur-containing compounds (a) and the mass percentage of oxalate complex anions (c) in the non-aqueous electrolyte are related by a / c < 0.05, it indicates that the content of sulfur-containing compounds is too low or the content of oxalate complex anions in the electrolyte is too high. If the value of a is too low, it is difficult to suppress the negative effects of oxalate complex anions participating in film formation, resulting in increased gas production and rapid impedance growth in the battery. If the value of c is too high, not only can its negative effects not be suppressed, but the film-forming effect of difluorophosphate cannot be highlighted because there is too much Li2CO3 and a reduced proportion of LiF in the earliest interfacial film.

[0021] When the ratio a / c > 15, the relationship between the mass percentage of sulfur-containing compounds (a) and the mass percentage of oxalate complex anions (c) in the non-aqueous electrolyte indicates that the content of sulfur-containing compounds is too high or the amount of oxalate complex anions in the electrolyte is too low. If the value of a is too high, although a highly stable and dense uniform film can be formed, the impedance of the positive and negative electrode films is too high, which intensifies battery heat generation and results in poor lithium-ion transport kinetics in the interface film. During fast charging, the battery is prone to lithium deposition, leading to rapid reaction and consumption of electrolyte and active lithium. If the value of c is too low, the film formed by difluorophosphate ions and sulfur-containing compounds may result in good stability but high impedance or low impedance but poor stability, failing to balance impedance and high-temperature performance.

[0022] Preferably, the relationship between the mass percentage of sulfur-containing compounds a and the mass percentage of difluorophosphate ions c in the non-aqueous electrolyte satisfies 0.1 ≤ a / c ≤ 10.

[0023] When the relationship between the mass percentage of difluorophosphate ions, the mass percentage of oxalate complex anions, and the adhesion force between the negative electrode material layer and the negative electrode current collector in the non-aqueous electrolyte, b / (c×d) < 0.05, it indicates that there are too few difluorophosphate ions, too many oxalate complex anions, or too much adhesion force between the negative electrode material layer and the negative electrode current collector. If the b value is too small, it is difficult to form a LiF-rich interface film, resulting in poor film stability. If the c value is too high, the film stability is also poor, and the battery is prone to gas generation and rapid impedance growth. If the d value is too large, it indicates that the amount of negative electrode binder is too large or it is enriched on the surface, which is not conducive to the electron conduction of the negative electrode and may even affect the film stability. At the same time, it will cause the performance of the negative electrode active material to be unable to be fully utilized, resulting in a lower actual capacity at the battery level.

[0024] When the relationship b / (c×d)>20, it indicates that there are too many difluorophosphate ions, too few oxalate complex anions, or too low adhesion between the negative electrode material layer and the current collector. If the c value is too low, the battery impedance cannot be effectively reduced, making it difficult to meet the performance requirements of low impedance and fast charging cycle. If the b value is too large, it indicates that too many difluorophosphate additives have been added. Too much LiF component will also degrade the impedance, and the additive may precipitate in the form of LiPO2F2 as a solid impurity, causing battery performance degradation. If the d value is too low, the negative electrode ohmic impedance may increase significantly, the battery polarization will increase, and the fast charging cycle will degrade.

[0025] Preferably, the relationship between the mass percentage of difluorophosphate ions (b), the mass percentage of oxalate complex anions (c), and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector in the non-aqueous electrolyte satisfies 0.1≤b / (c×d)≤5.

[0026] In the lithium-ion battery of this invention, the sulfur-containing compound can participate in the formation of a dense and uniform interfacial film at both the positive and negative electrodes, improving the film's stability and resistance to HF attack, thereby improving the battery's high-temperature performance. Furthermore, it also possesses stronger and more ionized F than proton H. -The ability to bind effectively suppresses the generation of HF and its negative effects on the interfacial film. Its film-forming potential is higher than that of difluorophosphate ions and oxalate complex anions, meaning its film-forming components are mainly distributed in the outer layer of the inorganic film. This protects the high-content Li₂CO₃ in the inner layer from direct contact with the liquid electrolyte to prevent gas generation, while further improving film stability and increasing the toughness of the outer inorganic film, reducing film damage caused by electrode volume changes during cycling. If the a value is too high, the battery impedance is too large, and the battery charge / discharge polarization and heat generation increase significantly, causing a series of negative effects such as lithium salt thermal decomposition and impedance increase, ultimately degrading the battery's electrochemical performance. If the a value is too low, it is difficult to protect the structure of the inner inorganic film rich in LiF and Li₂CO₃ components and reduce the acidity increase caused by oxalate, failing to fully utilize the film-forming effect of the oxalate complex anion and suppress its negative effects of gas generation and acidity increase. Specifically, in some embodiments of the present invention, the mass percentage 'a' of sulfur-containing compounds in the non-aqueous electrolyte is 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, or any combination of these values; preferably, the mass percentage 'a' of sulfur-containing compounds in the non-aqueous electrolyte is 0.05 to 0.5 wt%.

[0027] In the non-aqueous electrolyte of the lithium-ion battery of this invention, the difluorophosphate ions are derived from compounds containing difluorophosphate ions and the hydrolysis of lithium hexafluorophosphate. Difluorophosphate ions can participate in the formation of the SEI film, increasing the LiF content in the film composition, thereby improving the stability of the SEI film and reducing its impedance. If the b value is too high, difluorophosphate ions are easily precipitated from the electrolyte or cannot be completely dissolved, acting as impurities and foreign matter, causing uneven stress within the battery and degrading battery performance. Furthermore, an excessively high b value may result in an excessive amount of inorganic components in the interface film, degrading battery impedance. If the b value is too low, it is difficult to form a LiF-rich interface film, failing to improve battery impedance and high-temperature performance. Specifically, in some embodiments of the present invention, the mass percentage b of difluorophosphate ions in the non-aqueous electrolyte is 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, or any combination of these values; preferably, the mass percentage b of difluorophosphate ions in the non-aqueous electrolyte is 0.05 to 0.8 wt%.

[0028] In the non-aqueous electrolyte of the lithium-ion battery of the present invention, the mass percentage of difluorophosphate ions has the same meaning as the concentration of difluorophosphate ions; the present invention does not specifically limit the method for determining the mass percentage of difluorophosphate ions, and methods known in the art, such as ion chromatography, can be used. 19 FNMR, etc.

[0029] In the non-aqueous electrolyte of the lithium-ion battery of this invention, the oxalate complex anion participates in film formation, generating more Li2CO3 components, which then synergistically work with difluorophosphate ions. This not only generates a LiF-rich interfacial film but also ensures sufficient LiF / Li2CO3 interface content while maintaining low battery impedance. Furthermore, its film formation potential is lower than that of difluorophosphate ions, sulfur-containing compounds, and most commonly used electrolyte additives. This allows for the formation of an inorganic inner SEI film with a gradient in Li2CO3 content. This gradient structure increases the Li2CO3 content while minimizing the amount of Li2CO3 in the inorganic outer layer that comes into contact with the liquid electrolyte, preventing the dissolution and decomposition of Li2CO3. Additionally, fluorinated oxalate complex anions can also contribute to the formation of a LiF-rich interfacial film. If the c value is too high, the SEI film will contain excessive Li2CO3 components, and the electrolyte acidity will increase significantly. Li2CO3 easily decomposes at high temperatures or high voltages, producing CO or CO2 gas, resulting in uneven lithium insertion / extraction in the electrode-separated battery. Furthermore, Li2CO3's ability to isolate electrons is worse than LiF, leading to a thicker SEI film during formation, which actually degrades impedance. Increased acidity will damage the positive and negative electrode interface film and even corrode the electrode active materials, worsening battery impedance and high-temperature performance. If the c value is too low, the improvement in battery performance will be very limited. Specifically, in some embodiments of the present invention, the mass percentage c of oxalate complex anions in the non-aqueous electrolyte of the lithium-ion battery is 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, or any combination of these values; preferably, the mass percentage c of oxalate complex anions in the non-aqueous electrolyte of the lithium-ion battery is 0.05 to 0.5 wt%.

[0030] In the non-aqueous electrolyte of the lithium-ion battery of the present invention, the mass percentage of oxalate complex anions has the same meaning as the concentration of oxalate complex anions; the present invention does not specifically limit the method for determining the mass percentage of oxalate complex anions, and methods known in the art, such as ion chromatography, can be used. 19 F NMR, etc.

[0031] In the lithium-ion battery negative electrode of this invention, excessively low adhesion between the negative electrode material layer and the negative electrode current collector affects the electron conduction between them, increasing the battery impedance and polarization during charge and discharge. This has a significant negative impact on the battery's fast-charge cycle performance and charging capacity during fast charging. As the d-value increases, the resistance of electrons across the interface between the negative electrode current collector and the negative electrode material layer decreases, and the rate of charge exchange between active ions and electrons on the surface of the negative electrode active material increases, resulting in better kinetic performance of the battery. However, an excessively large d-value indicates an excessive binder content in the negative electrode material layer, or a high concentration of binder on the surface of the negative electrode active material, or an excessively large spread area of ​​binder on the negative electrode current collector. This is detrimental to electron conduction in the negative electrode and may even affect film stability, significantly degrading the battery's kinetic and cycle performance. Furthermore, an excessive binder content in the negative electrode material layer also affects the actual capacity utilization of the battery. Specifically, in some embodiments of the present invention, the adhesion force d between the negative electrode material layer and the negative electrode current collector is 0.5 N / m, 0.8 N / m, 1 N / m, 1.1 N / m, 1.2 N / m, 1.3 N / m, 1.4 N / m, 1.5 N / m, 1.8 N / m, 1.9 N / m, 2.0 N / m, 2.1 N / m, 2.2 N / m, 2.5 N / m, 2.6 N / m, 2.8 N / m, 2.9 N / m, 3.0 N / m, 3.1 N / m, 3.2 N / m, 3.3 N / m, 3.5 N / m, 3.6 N / m, 3.8 N / m, 4.0 N / m, 4.1 N / m, 4.2 N / m, 4.5 N / m, 4. The values ​​are 0.6 N / m, 4.8 N / m, 5 N / m, 5.1 N / m, 5.2 N / m, 5.5 N / m, 5.6 N / m, 5.8 N / m, 6.0 N / m, 6.5 N / m, 7.0 N / m, 7.5 N / m, 8.0 N / m, 8.5 N / m, 9.0 N / m, 9.5 N / m, 10 N / m, 11 N / m, 12 N / m, 13 N / m, 14 N / m, 14.5 N / m, 15 N / m, or any combination of these values; preferably, the adhesion force d between the negative electrode material layer and the negative electrode current collector is 1 to 5 N / m; more preferably, the adhesion force d between the negative electrode material layer and the negative electrode current collector is 1 to 3 N / m.

[0032] Therefore, only the mass percentage 'a' of sulfur-containing compounds in the non-aqueous electrolyte and the difluorophosphate ions [PO2F2] in the non-aqueous electrolyte are considered. -The mass percentage of the three substances (b), the mass percentage of oxalate complex anions in the non-aqueous electrolyte (c), and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector must satisfy 0.05≤a / c≤15, 0.05≤b / (c×d)≤20; and 0.01≤a≤1, 0.01≤b≤1.2, 0.01≤c≤0.8, 0.5≤d≤15. Only in this way can the characteristics of the three substances before and after film formation and the film-forming components be fully utilized. Combined with the pre-controlled formation of a high adhesion force between the negative electrode material layer and the negative electrode current collector, the degradation caused by micro-gas production can be offset, and the separation of the negative electrode material layer and the current collector can be avoided. This achieves the best film stability while maintaining low impedance, making up for their respective deficiencies, so that the battery has low impedance and excellent high-temperature fast-charging cycle performance.

[0033] Specifically, in some embodiments of the present invention, the oxalate complex anion is selected from at least one of difluorooxaloborate ion, bis(oxaloborate) anion, and difluorodiooxalophosphate ion. In the non-aqueous electrolyte of the present invention, monovalent and divalent cations can be used as counterions to the oxalate complex anion; preferably, the monovalent cations are lithium ions, sodium ions, and potassium ions, and the divalent cations are magnesium ions and calcium ions. Other monovalent or divalent cations are also within the scope of protection of the present invention.

[0034] Specifically, in some embodiments of the present invention, the compound containing difluorophosphate ions is selected from at least one of lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, calcium difluorophosphate, and magnesium difluorophosphate. In the non-aqueous electrolyte of the present invention, monovalent and divalent cations can be used as counterions to difluorophosphate ions; preferably, the monovalent cation is lithium ion, and the divalent cation is magnesium ion. Other monovalent or divalent cations are also within the scope of protection of the present invention and will not be elaborated here.

[0035] Specifically, in some embodiments of the present invention, the lithium salt further includes lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPO₂F₂, LiBF₄, LiBOB, LiSbF₆, LiAsF₆, LiCF₃SO₃, LiDFOB, LiDFOP, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃, LiN(SO₂C₂F₅)₂, LiCl, LiBr, LiI, LiClO₄, and LiB₂. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, and lithium tetraphenylborate.

[0036] Specifically, in some embodiments of the present invention, the organic solvent includes at least one of cyclic carbonate solvents, linear carbonate solvents, carboxylic acid ester solvents, and ether solvents.

[0037] In some preferred embodiments, the cyclic carbonate solvent includes at least one of vinylene carbonate, propylene carbonate, ethylene carbonate, and butene carbonate.

[0038] In some preferred embodiments, the linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

[0039] In some preferred embodiments, the carboxylic acid ester solvent includes at least one selected from methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and ethyl trimethylacetate.

[0040] In some preferred embodiments, the ether solvent includes at least one of ethylene glycol dimethyl ether, 1,3-dioxolane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0041] Specifically, in some embodiments of the present invention, the additive further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0042] In some preferred embodiments, the cyclic sulfate compound includes at least one of 4-methyl vinyl sulfate, vinyl sulfate, and propylene sulfate.

[0043] In some preferred embodiments, the sulfonyl lactone compound includes at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, and propenyl-1,3-sulfonyl lactone.

[0044] In some preferred embodiments, the cyclic carbonate compound includes at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, and a compound represented by structural formula 1 below:

[0045]

[0046] In the structural formula 1 shown, R 21 R 22 R 23 R 24 R 25 R 26Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0047] In some preferred embodiments, the compound of structural formula 1 includes at least one of the compounds shown in compounds 1-1 to 1-6 below:

[0048]

[0049] In some preferred embodiments, the phosphate ester compound includes at least one of the compounds represented by structural formula 2:

[0050]

[0051] In structural formula 2, R 31 R 32 R 33 Each is independently selected from saturated hydrocarbon groups, unsaturated hydrocarbon groups, and halogenated hydrocarbon groups of C1-C5; more preferably, the compound represented by structural formula 2 includes at least one of the following: triargyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0052] In some preferred embodiments, the borate ester compound includes at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate.

[0053] In some preferred embodiments, the nitrile compound includes at least one selected from succinic anhydride, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebacate.

[0054] In some embodiments, the content of the auxiliary additive is 0.01 wt% to 10 wt%, based on the total mass of the non-aqueous electrolyte as 100%. Specifically, the content of any optional substance in the auxiliary additive can be 0.01 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.5 wt%, 5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or any combination of these values.

[0055] Specifically, in some embodiments of the present invention, the negative electrode material layer includes a negative electrode active material, which includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, mesophase micro carbon spheres, silicon, silicon oxide, silicon-carbon composite or metallic lithium.

[0056] Specifically, in some embodiments of the present invention, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent.

[0057] The negative electrode binder includes one or more of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0058] The negative electrode conductive agent includes one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0059] Specifically, in some embodiments of the present invention, the negative electrode current collector includes a metallic material capable of conducting electrons, preferably, the negative electrode current collector includes one or more of aluminum, nickel, tin, copper, and stainless steel.

[0060] Specifically, in some embodiments of the present invention, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material may include LiFe. 1-x’ M' x’ PO4, LiMn2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z One or more of O2, wherein M' is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1. The positive electrode active material may also include one or more of sulfides, selenides, and halides. More preferably, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0061] Specifically, in some embodiments of the present invention, the positive electrode further includes a positive current collector, and the positive electrode material layer is disposed on the surface of the positive current collector. The material of the positive current collector may be the same as that of the negative current collector, and will not be described in detail here.

[0062] Specifically, in some embodiments of the present invention, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are blended to obtain the positive electrode material layer. The positive electrode binder and the positive electrode conductive agent can be the same as the negative electrode binder and the negative electrode conductive agent, respectively, and will not be described in detail here.

[0063] In the lithium-ion battery of the present invention, a separator is provided between the positive electrode and the negative electrode. The separator can be a conventional separator, such as a ceramic separator, a polymer separator, a non-woven fabric separator, an inorganic-organic composite separator, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and triple-layer PP / PE / PP separators.

[0064] In the non-aqueous electrolyte of the lithium-ion battery of the present invention, a sulfur-containing compound is used as an additive. The mass percentages of the sulfur-containing compound (a), difluorophosphate ions (b), and oxalate complex anions (c) in the non-aqueous electrolyte, and the relationships between the negative electrode material layer and the negative electrode current collector (d) satisfy 0.05 ≤ a / c ≤ 15, 0.05 ≤ b / (c × d) ≤ 20; and 0.01 ≤ a ≤ 1, 0.01 ≤ b ≤ 1.2, 0.01 ≤ c ≤ 0.8, 0.5 ≤ d ≤ 1. 5. It can fully leverage the advantages of oxalate complex anions in reducing battery impedance and forming a highly stable LiF-rich interface film. At the same time, it can regulate the adhesion between the negative electrode material layer and the negative electrode current collector to counteract the impact of Li2CO3 decomposition gas production on the battery. By utilizing the order of film formation of different materials and the characteristics of the components, it can control the formation of a low-impedance and stable negative electrode interface film. Combined with the pre-controlled formation of a high adhesion between the negative electrode material layer and the negative electrode current collector, it can counteract the degradation of the battery caused by micro-gas production, thus achieving a high-quality lithium-ion battery that balances impedance and fast-charging cycle performance. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0066] In the embodiments and comparative examples of the present invention, one of the compounds shown in Table 1 is used as a non-aqueous electrolyte additive.

[0067] Table 1

[0068]

[0069]

[0070] Example 1

[0071] The method for preparing the lithium-ion battery in this embodiment includes the following steps:

[0072] 1) Preparation of the positive electrode sheet:

[0073] LiNi 0.5 Mn 0.3 Co 0.2 O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed uniformly at a mass ratio of 97:1.5:1.5, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, and after drying, calendering, and vacuum drying, a positive electrode material layer is obtained. Aluminum leads are then welded on using an ultrasonic welding machine to obtain the positive electrode sheet.

[0074] 2) Preparation of the negative electrode sheet:

[0075] Weigh out the materials according to the following ratio for negative electrode preparation: graphite (Shanghai Shanshan, FSN-1): conductive carbon (superP): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 96.3:1.0:1.2:1.5 (mass ratio). Add CMC to pure water with a solid content of 1.5% and stir for 120 minutes until homogeneous to prepare a transparent CMC solution. Add conductive carbon (superP) to the CMC solution and stir for 90 minutes until homogeneous to prepare a conductive adhesive. Continue to add graphite to the conductive adhesive and stir until homogeneous to obtain the required negative electrode slurry. Coat the prepared negative electrode slurry evenly on copper foil, dry, roll, die-cut or slit, and weld nickel leads with an ultrasonic welding machine to obtain the negative electrode sheet.

[0076] The adhesion between the negative electrode material layer and the negative electrode current collector was tested. The test method was as follows: The adhesion between the negative electrode material layer and the negative electrode current collector can be tested with reference to the national standard GB / T2790-1995, "Test Method for 180° Peel Strength of Adhesives". Specifically, a high-speed rail tensile testing machine was used to perform the 180° peel force test at a peeling speed of 50 mm / min. The average peel force collected when a 60 mm long negative electrode sheet was completely peeled from the negative electrode current collector was taken as the adhesion between the negative electrode material layer and the negative electrode current collector. The test results were recorded in Table 2.

[0077] 3) Preparation of electrolyte:

[0078] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Then, lithium hexafluorophosphate and additives were added. The concentration of lithium hexafluorophosphate in the non-aqueous electrolyte was 1.02 mol / L. The types and contents of each additive are shown in Table 2.

[0079] 4) Preparation of the diaphragm:

[0080] A three-layer separator membrane made of polypropylene, polyethylene, and polypropylene is used, with a thickness of 20μm.

[0081] 5) Battery assembly:

[0082] The prepared positive electrode, negative electrode and separator are assembled into a stacked soft-pack battery cell.

[0083] 6) Electrolyte injection and formation of battery cells

[0084] In a glove box with the dew point controlled below -40°C, the electrolyte prepared above was injected into the cell, vacuum sealed, and left to stand for 72 hours. Then, the first charge was performed according to the following steps: 0.05C constant current charging for 180 min, 0.1C constant current charging for 120 min, 0.2C constant current charging for 120 min, followed by a second vacuum sealing, and then a full charge at 0.2C (100% SOC). After resting at room temperature for 72 hours, a full discharge at 0.2C (0% SOC) was performed.

[0085] Examples 2-33 and Comparative Examples 1-31

[0086] This embodiment and comparative example are used to illustrate the lithium-ion battery disclosed in this invention. They include most of the operating steps in the above embodiment 1, but differ in that: the composition and content of additives in the non-aqueous electrolyte, and the adhesion between the negative electrode material layer and the negative electrode current collector of the battery negative electrode, as shown in Table 2.

[0087] Table 2

[0088]

[0089]

[0090]

[0091]

[0092] Among them: LiODFP-lithium difluorodioxalate phosphate, LiODFB-lithium difluorodioxalate phosphate, LiBOB-lithium dioxalate borate, DTD-ethylene sulfate, PS-1,3-propane sulfonate lactone, VC-ethylene carbonate.

[0093] The lithium-ion batteries prepared in Examples 1-33 and Comparative Examples 1-31 were subjected to the following performance tests using the following methods:

[0094] 1. High-temperature fast charging cycle performance test:

[0095] At 45°C, the lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current and constant voltage of 1C (cutoff current 0.05C) and discharged at a 1C rate for three cycles. The capacity of the last cycle was taken as the initial 100% SOC capacity. After being charged at a constant current of 4C to 80% SOC, they were fully charged at a constant current and constant voltage of 1C (cutoff current 0.05C) and discharged at a 1C rate. Full charge and discharge cycle tests were performed within the commonly used charge and discharge cutoff voltage range for the corresponding system (e.g., 3-4.2V for NCM523 / artificial graphite system) until the capacity of the lithium-ion battery decayed to 80% of the initial capacity, and the number of cycles was recorded.

[0096] 2. Internal resistance test at 0℃:

[0097] Charge the battery at a constant current to 50% of its capacity at room temperature (25℃), then set the temperature to 0℃ and maintain this temperature for 6 hours.

[0098] Charge at 0.1C constant current for 10 seconds and then let stand for 40 seconds; discharge at 0.1C constant current for 10 seconds and then let stand for 40 seconds, and record the termination voltage V1.

[0099] Charge at 0.2C constant current for 10s and then let stand for 40s; discharge at 0.2C constant current for 10s and then let stand for 40s, and record the termination voltage V2.

[0100] Charge at 0.5C constant current for 10 seconds and then let stand for 40 seconds; discharge at 0.5C constant current for 10 seconds and then let stand for 40 seconds, and record the termination voltage V3.

[0101] Plot a straight line with current as the x-axis and voltage as the y-axis. The slope of the line is the impedance at 0°C.

[0102] (1) The test results of Examples 1-19 and Comparative Examples 4-24 are shown in Table 3.

[0103] Table 3

[0104]

[0105]

[0106] As can be seen from the test results in Table 3, the lithium-ion battery of the present invention, using sulfur-containing compounds as additives, and further controlling the relationship between the mass percentage content (a) of sulfur-containing compounds, the mass percentage content (b) of difluorophosphate ions, the mass percentage content (c) of oxalate complex anions, and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector in the non-aqueous electrolyte, satisfies 0.05≤a / c≤15, 0.05≤b / (c×d)≤20; and 0.01≤a≤1, 0.01≤b≤1.2, 0.01≤c≤0.8, 0.5≤d≤15, can achieve both low impedance and fast charging cycle performance.

[0107] As can be seen from the test results of Example 1 and Comparative Examples 4-24, when any one or more of the following parameters in the non-aqueous electrolyte do not meet the specified range, or when at least one of a / c or b / (c×d) is too large or too small, it is impossible to simultaneously achieve low impedance and fast charging cycle performance of the lithium-ion battery. This indicates that there is a strong correlation between the mass percentage of sulfur-containing compounds (a), the mass percentage of difluorophosphate ions (b), the mass percentage of oxalate complex anions (c), and the adhesion force between the electrode material layer and the negative electrode current collector (d) in reducing lithium-ion battery impedance and optimizing lithium-ion fast charging cycle performance.

[0108] In particular, a comparison of the test results of Example 1 and Comparative Examples 17-20 shows that if the adhesion force d between the negative electrode material layer and the negative electrode current collector does not meet the specified range, the battery performance will deteriorate to some extent. This is because an excessively large d is detrimental to the electron conduction of the negative electrode and affects the effect and stability of oxalate complex anions participating in film formation; while an excessively small d will increase battery impedance and polarization during charging and discharging. Furthermore, changes in d will cause changes in the b / (c×d) relationship, indicating that the adhesion force between the negative electrode material layer and the negative electrode current collector, in conjunction with sulfur-containing compounds, difluorophosphate ions, and oxalate complex anions, affects the impedance and fast-charging cycle performance of the lithium-ion battery.

[0109] (2) The test results of Examples 20-25 and Comparative Examples 25-28 are shown in Table 4.

[0110] Table 4

[0111]

[0112] As shown in Table 4, the test results of Examples 20-25 and Comparative Examples 25-28 indicate that for the lithium-ion battery of the present invention, when different positive electrode active materials are used, the impedance performance and high-temperature performance of the lithium-ion battery can be optimized when the mass percentage of sulfur-containing compounds (a), the mass percentage of difluorophosphate ions (b), the mass percentage of oxalate complex anions (c), and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector meet the corresponding conditions. Under the same positive electrode active material, when any parameter among the following—mass percentage of sulfur-containing compounds (a), mass percentage of difluorophosphate ions (b), mass percentage of oxalate complex anions (c), and adhesion force (d) between the negative electrode material layer and the negative electrode current collector—does not meet the corresponding conditions, it will affect the battery performance. This demonstrates that the battery system of the present invention has universal applicability to different positive electrode active materials.

[0113] (3) The test results of Examples 1, 31-33 and Comparative Examples 29-31 are shown in Table 5.

[0114] Table 5

[0115]

[0116] As shown in Table 5, the test results of Examples 1 and 31-33 indicate that for the lithium-ion battery of this invention, when different tricyclic compounds are used as sulfur-containing compounds in the non-aqueous electrolyte, the following conditions are met: the mass percentage of sulfur-containing compounds (a), the mass percentage of difluorophosphate ions (b), the mass percentage of oxalate complex anions (c), and the adhesion force (d) between the negative electrode material layer and the negative electrode current collector. Simultaneously, the relationships a / c and b / (c×d) also meet the corresponding conditions, thus optimizing the impedance performance and fast-charging cycle performance of the lithium-ion battery. As shown in Table 5, the test results of Examples 1 and 29-31 indicate that when a bicyclic compound is used as the sulfur-containing compound, it is impossible to suppress the deteriorating effect of lithium salts and oxalate complex anions on battery performance, and the battery impedance and fast-charging cycle performance cannot be improved. This further illustrates the optimization effect of the tricyclic compound used in the sulfur-containing compound on battery performance.

[0117] (4) The test results of Examples 1 and Examples 26-27 are shown in Table 6.

[0118] Table 6

[0119]

[0120] As shown in Table 6, the test results of Examples 1 and 26-27 indicate that by using different compounds containing oxalate complex anions, when the mass percentages of sulfur-containing compounds (a), difluorophosphate ions (b), oxalate complex anions (c), and the adhesion force between the negative electrode material layer and the negative electrode current collector (d) meet the corresponding conditions, the impedance performance and high-temperature performance of lithium-ion batteries can be optimized. This demonstrates that the battery system of the present invention has universal applicability to different compounds containing oxalate complex anions.

[0121] (5) The test results of Examples 1, 28-30, and Comparative Examples 1-3 are shown in Table 7.

[0122] Table 7

[0123]

[0124] As can be seen from the test results of Examples 1 and 28-30 in Table 7, the lithium-ion battery of the present invention, with the addition of additives such as ethylene sulfate (DTD), 1,3-propanesulfonyl lactone (PS), and vinylene carbonate (VC) to the non-aqueous electrolyte, can further optimize the impedance performance and fast-charging cycle performance of the lithium-ion battery, indicating that there is a complementary effect between the additives of the present invention and other additives.

[0125] As can be seen from the test results of Example 1 and Comparative Examples 1-3, when auxiliary additives are used to replace sulfur-containing compounds or compounds containing oxalate complex anions in non-aqueous electrolytes, the additives do not form a good synergistic effect, resulting in poor performance in suppressing the impedance increase of lithium-ion batteries and improving fast-charge cycle performance. This indicates that the lithium-ion battery in the system of this invention improves the impedance performance and fast-charge cycle performance of lithium-ion batteries through the use of specific additives and their interaction with the adhesive force between the negative electrode material layer and the negative electrode current collector.

[0126] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that, Includes positive electrode, negative electrode, and non-aqueous electrolyte; The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on the surface of the negative electrode current collector; The non-aqueous electrolyte includes lithium salts, organic solvents, sulfur-containing compounds, difluorophosphate ions, and oxalate complex anions; The sulfur-containing compound includes at least one of the following compounds: The lithium-ion battery meets the following conditions: 0.05≤a / c≤15, 0.05≤b / (c×d)≤20, 0.01≤a≤1, 0.01≤b≤1.2, 0.01≤c≤0.8, 0.5≤d≤15; Where 'a' represents the mass percentage of sulfur-containing compounds in the non-aqueous electrolyte, in wt%; b represents the mass percentage of difluorophosphate ions in the non-aqueous electrolyte, in wt%; c represents the mass percentage of oxalate complex anions in the non-aqueous electrolyte, in wt%; d represents the bonding force between the negative electrode material layer and the negative electrode current collector, measured in N / m, and is obtained by testing according to the national standard GB / T2790-1995, "180° Peel Strength Test Method for Adhesives".

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies the following conditions: 0.1≤a / c≤10, 0.1≤b / (c×d)≤5.

3. The lithium-ion battery according to claim 1, characterized in that, The mass percentage (a) of sulfur-containing compounds in the non-aqueous electrolyte is 0.05~0.5wt%.

4. The lithium-ion battery according to claim 1, characterized in that, The mass percentage b of difluorophosphate ions in the non-aqueous electrolyte is 0.05~0.8wt%.

5. The lithium-ion battery according to claim 1, characterized in that, The mass percentage (c) of oxalate complex anions in the non-aqueous electrolyte is 0.05~0.5wt%.

6. The lithium-ion battery according to claim 1, characterized in that, The adhesion force d between the negative electrode material layer and the negative electrode current collector is 1~5 N / m.

7. The lithium-ion battery according to claim 1, characterized in that, The oxalate complex anion is selected from at least one of difluorooxaloborate anion, bis(oxaloborate) anion, and difluorodi(oxaloborate) phosphate anion.

8. The lithium-ion battery according to claim 1, characterized in that, The organic solvent includes one or more of cyclic carbonates, linear carbonates, carboxylic acid esters, and ethers; and / or, The cyclic carbonates include one or more selected from vinylene carbonate, propylene carbonate, ethylene carbonate, and butene carbonate; and / or, The linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate; and / or, The carboxylic acid ester includes one or more selected from methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and ethyl trimethylacetate; and / or, The ethers include one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

9. The lithium-ion battery according to claim 1, characterized in that, The non-aqueous electrolyte further includes auxiliary additives, which include at least one selected from cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate ester compounds, and nitrile compounds; and / or, Based on the total mass of the non-aqueous electrolyte as 100%, the content of the auxiliary additives is 0.01%~10%; and / or, The cyclic sulfate compounds include at least one of 4-methylvinyl sulfate, vinyl sulfate, and propylene sulfate; and / or, The sulfonyl lactone compounds include at least one selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, and propenyl-1,3-sulfonyl lactone; and / or, The cyclic carbonate compounds include at least one of the following: vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, and a compound represented by structural formula 1: Structural Formula 1 In the structural formula 1 shown, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, C1-C5 group; and / or, The phosphate ester compounds include at least one of the compounds shown in structural formula 2: Structural Formula 2 In structural formula 2, R 31 R 32 R 33 Each group is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, and haloalkyl groups; and / or, The borate ester compounds include at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate; and / or, The nitrile compounds include at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitol.

10. The lithium-ion battery according to claim 1, characterized in that, The negative electrode material layer includes a negative electrode active material, which includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, mesophase micro carbon spheres, silicon, silicon oxide, silicon-carbon composite, or metallic lithium.

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